This weekend I was asked to contribute to The New York Times' Room for Debate. I was kind of under the impression that the question was, "Is the Kerry-Graham-Lieberman bill worth passing?" Apparently, though, it was, "Does the climate bill stand a chance?" Obviously those questions have different answers! Mine was geared to the former, everybody else's the latter, but oh well. Other answers were provided by:

The climate and energy bill being developed by John Kerry, Joe Lieberman, and (depending on the hour) Lindsey Graham isn't very popular on the green left. Climate campaigners lament that the senators have capitulated to fossil fuel companies, proposing to subsidize the very industries that are polluting the atmosphere and, as we speak, more or less destroying the Gulf of Mexico. They say the bill won't come close to solving the problem.

And they're right. That makes those of us who still believe the bill is worth passing somewhat unpopular -- sellouts, corrupt insiders and so on. Why would someone who recognizes the scope and severity of the problem support a bill that won't solve it?

There's a complicated answer to that question, but there's also a simple one, and it's this: I am optimistic about decarbonization. Despite conventional wisdom to the contrary, reducing emissions will be relatively fast and inexpensive. There are huge opportunities for low-cost (or negative-cost) emission reductions just waiting to be exploited.

Right now, policy is being made out of fear: fear by the private sector that decarbonization will be a crushing burden; fear by consumers that their energy prices will skyrocket; fear by politicians that the project will prove electorally unpopular. Campaigners can organize marches, think tanks can put out reports, scientists can issue dire warnings, but ultimately, that fear simply can't be overcome in advance. The only way to overcome it is through experience.

Because the bill contains two crucial elements -- a declining cap on emissions and a floor on the price of carbon -- here's what will happen: the price for carbon will sit on the floor and, despite that, the U.S. will sail past its (tepid, cautious) short-term target. In 2020, buoyed by success, backed by newly powerful clean energy constituencies, the political system will revisit the issue and pass more ambitious targets. The same thing will happen in 2030. And in 2040. And 2050. Success will breed success. Oil and coal won't be able to compete and eventually politicians will get sick of subsidizing them.

If you don't share that optimism -- if you think decarbonization is going to be a grinding, difficult, expensive process -- then you have every right to be horrified by the bill's inadequacy. But then, you don't have much to be optimistic about, since the likelihood of a substantially stronger bill is vanishingly small any time in the foreseeable future.

But if you do share that optimism, you'll agree that putting a system in place and getting started is more important, in the grand scheme of things, than getting this iteration of the legislation just right. There's been more than enough talking; let's let action make the argument for us.

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Now, I only had 300 words. Obviously things are more complicated than this. For one thing, we'd be way better off, and move way faster, if the declining cap and carbon price floor were accompanied by a strong renewable energy standard, a strong energy efficiency standard, and a massive program of public investment in clean energy RD&D. Those elements of the KGL bill are probably going to be severely lacking, and I'm sure I will do plenty of wailing and garmet-rending when I see it.

What it comes down to, though, is that lots of greens have been hoping, striving, and pushing for a long time for a Big Bill -- the one, true bill that has scientifically legitimate targets and tight, loophole-free policy mechanisms. The one that can solve the problem. But for many reasons, some valid, some not, Congress rarely passes Big Bills. They almost never solve problems in a single, grand stroke. Congress works incrementally. Ultimately we're going to have to accept some increment, some partial solution, just to get underway. There isn't another choice.